Signals from a substrate package travel to another substrate package attached to a common motherboard through the sockets and motherboard. Signals traveling on this path are susceptible to signal degradation and losses due to on-die parasitics, transmission loss, return loss and cross talks. Flex cable interconnection provides improved signal transmission quality and transfer rate.
FIG. 1A illustrates a cross sectional view of a known inter-package flex cable connection. Substrate package 120 includes die 104 attached to substrate body 102 via die bumps 105. Substrate package 120 is mounted on socket 108. Socket 108 has socket contacts 109 soldered to solder balls 110. Solder balls 110 are reflowed to form connection with motherboard 112. Substrate package 120 is interconnected with another substrate package 130 attached to motherboard 112 by way of flex cable 114. Flex cable 114 is attached to substrate packages 120, 130 by way of connector 106. Connector 106 is soldered on substrate body 102 and forms part of substrate body 102. Connector 106 and flex cable 114 are commercially available. Signals between substrate packages 120, 130 are transmitted via flex cable 114 without having to route through socket 108 or motherboard 112.
FIG. 1B illustrates another known inter-package flex cable connection. In relation to substrate package 120, flex cable 114 is inserted between socket 108 and motherboard 112. One end of flex cable 114 is soldered to socket contacts 109 while the other end of flex cable 114 is soldered to the land side of substrate package 130. Signals between substrate packages 120, 130 are transmitted via flex cable 114.